The processing of signals or data is one of the cores of the information chain from production to application. More and more signals should be processed digitally in the big data era. Rapid and massive advances in digital signal processing (DSP) technology have been achieved over the past several decades. DSP technology revolutionized the electronics and opto-electronics industries. DSP technology is almost an all-embracing field and is advancing with each passing day. The classical application areas of DSP such as telecommunications, speech and image processing continue to be the main contributor to its growth. This book compiles cutting-edge research in several elementary and advanced topics in DSP, focusing on areas such as filter design algorithms, hardware/software techniques, and their applications. This book has a special emphasis on the modeling and design of optical communication filters. Use of well-developed DSP techniques and algorithms to design the wavelength division multiplexing (WDM) devices is a wise use of existing technology. The authors also share several of their thoughts concerning the practical DSP systems. The DSP theory and hardware for obscured object identification, and its applications in the intelligent baggage scanners are introduced systematically. This book will be helpful for students, researchers and engineers in the DSP fields to understand the basic knowledge and techniques of software, hardware, devices, and systems.